The invention relates to a method of truing-up the four faces of a piece of wood exhibiting squared cross section, and a relative machine unit.
The art field of woodworking machinery embraces a type of unit by which workpieces, and typically, longitudinal battens of essentially regular initial section, can be trued up and planed to size.
The operation of truing and surfacing a workpiece of squared section consists in removing wood from its four longitudinal faces by mechanical means. This done, i.e. with the cross-sectional dimensions being substantially to final requirements and the profile faultlessly square or rectangular, the work can be conveyed forward to successive tool stations where it is finished off and molded to a given shape, or perhaps matched with other components and glued.
In the case of further shaping, the workpiece might be tenoned, for example, in readiness for assembly as part of a door or window fixture, in which case the final step will be that of rounding off certain of the longitudinal edges, or sinking mortises in one or more of the faces.
In the case of glued pieces, these may constitute the component parts of boards, or other items of larger dimensions. In effect, there are significant practical and cost advantages in preparing a number of small battens to construct a larger board, most especially from the standpoint of economizing on materials; the economy will be evident when one considers that a finished item free of defects such as knots, splits etc. is more easily obtained from small pieces than from large.
Conventional machinery, equipment or units for truing-up the four faces of square-section work substantially comprise four planing tools, located in sequence along the path followed by the work: one beneath, with a horizontally disposed axis; one on the right flank with a vertically disposed axis; one on the left flank, also vertical; and a final horizontal tool positioned over the work, in short: bottom horizontal, vertical right, vertical left and top horizontal.
Such a unit also includes two tables, one on either side of the bottom tool (preceding and beyond), and a system of power driven feed rollers located above and operating in conjunction with the table beyond the bottom planer.
Thus, as each workpiece is fed in (manually or automatically, as may be) and advanced along the first table, the bottom face is planed to provide a reference for the remaining steps of the procedure; the work then passes onto the second table, which is aligned with the crest of the rotating bottom planer tool, and into contact with the overhead feed rollers which propel it forward through the tool stations that plane the right and the left faces and the top.
The various tools and feed systems are driven by individual respective motors, or, less typically, the tools are driven in pairs by one horizontally disposed motor and one vertically disposed motor, respectively.
Machines of the type thus outlined are beset by the drawback of a limited range of working adjustment, however, and of the fact that the finish produced on the right and left hand faces is not well suited to receive glue, should the workpiece be destined for subsequent bonding. More exactly, the vertical tools in these conventional machines are planers, just like the horizontal tools, and both produce a final surface that is smooth, and undulated through given stretches.
By contrast, experience in the field has shown that the surface best suited for bonding is that cut by a blade, i.e by a saw blade: a sawn cut does not compress the pores of the timber in the same way as a planing pass; instead, the surface is roughened, and thus better able to absorb the adhesive applied to it in correct fashion. Moreover, the undulations left by planing permit the formation of a film of glue between matched and bonded surfaces, which is visible from the outside and spoils the appearance of the finished item.
Accordingly, the object of the present invention is to set forth a method of truing the four faces of a piece of wood in such a way as to ensure that no splinters are produced, and that the side faces of any two pieces are rendered suitable for bonding with adhesive one to another, whilst retaining the levels of accuracy currently obtainable with a unit of conventional design.
Another object of the invention, gained by adoption of the constructional design of a unit as envisaged herein, is to provide machinery of singularly low manufacturing and running costs, ensured not least by virtue of its low power specification.